BMA255 datasheet(16/119 Pages) BOSCH

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BMA255

Data sheet

Page 16

BST-BMA255-DS004-05 | Revision 1.2 | August 2014

Bosch Sensortec

third parties. BOSCH and the symbol are registered trademarks of Robert Bosch GmbH, Germany.

Note: Specifications within this document are subject to change without notice.

State

Sleep phase

Active phase

SLEEP

ACTIVE

Figure 3: Timing Diagram for low-power mode 1/2, EDT

When (0x12) sleeptimer_mode is set to ‘1’, the equidistant-sampling mode (EST) is selected.

The use of the EST mode is recommended when the FIFO is used since it ensures that

equidistant samples are sampled into the FIFO regardless of whether the active phase is

extended by active interrupt engines or interface activity. In EST mode the sleep time tSLEEP is

defined as shown in Figure 4. The FIFO sampling time tSAMPLE is the sum of the sleep time tSLEEP

and the sensor data sampling time tSSMP. Since interrupt engines can extend the active phase to

exceed the sleep time tSLEEP, equidistant sampling is only guaranteed if the bandwidth has been

chosen such that 1/(2 * bw) = n * tSLEEP where n is an integer. If this condition is infringed,

equidistant sampling is not possible. Once the sleep time has elapsed the device will store the

next available sample in the FIFO. This set-up condition is not recommended as it may result in

timing jitter.

State

Sleep phase

Active phase

SLEEP

SAMPLE

Sampled into FIFO

SSMP

Figure 4: Timing Diagram for low-power mode 1/2, EST

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